1. Field of the Invention
The present invention relates to vehicle velocity control apparatus and method for an automotive vehicle (hereinafter, also called a host vehicle) having a function of following a preceding vehicle which is traveling ahead of the vehicle on the same traffic lane.
2. Description of the Related Art
A U.S. Pat. No. 6,249,738 B1 issued on Jun. 19, 2001 (which corresponds to a Japanese Patent Application First Publication No. Heisei 11-334552 published on Dec. 7, 1999) exemplifies a previously proposed preceding vehicle following control apparatus in which the host vehicle automatically follows the preceding vehicle, during a high-speed run, in a vehicle velocity range (for example, 40 Km/h to 110 Km/h) equal to or higher than a predetermined vehicle velocity. In such a previously proposed preceding vehicle following control apparatus as described in the above-described United States Patent, the vehicle velocity of the host vehicle at a time point at which a vehicular driver operates a switch is an upper limit of a controllable vehicle velocity range within which the following control is executed and, when no preceding vehicle is present, a cruise run (constant speed traveling) is carried out at the upper limit value of the controllable vehicle velocity range.
In addition, a Japanese Patent Application First Publication No. Heisei 10-205367 published on Aug. 4, 1998 exemplifies a previously proposed congestion-oriented preceding vehicle following control apparatus. In this previously proposed congestion-oriented preceding vehicle following control apparatus, during a traffic congestion, the host vehicle automatically follows the preceding vehicle within a vehicle velocity range which is equal or below a predetermined vehicle velocity.
However, for the former and latter previously proposed preceding vehicle following control apparatuses, a different control is executed when no preceding vehicle is present but the same contents of control are executed in respect of making the host vehicle follow the preceding vehicle when the preceding vehicle is detected to be present.
Therefore, suppose that, in order to architect a vehicle velocity control system having both of the functions that the preceding vehicle following controlling apparatus and the congestion-oriented following controlling apparatus have, two controls are automatically switched therebetween on the basis of a vehicle velocity of the host vehicle in such a way that one of the controls which is used in the former previously proposed preceding vehicle following control apparatus is executed when the vehicle velocity of the host vehicle is equal to or higher than a switching host vehicle velocity value and the other of the controls which is used in the latter congestion-oriented following control apparatus when the velocity of the host vehicle is below the switching host vehicle velocity value.
However, for example, when the preceding vehicle is present with the velocity of the host vehicle approximately around the switching vehicle velocity value, a motion of the host vehicle remains unchanged even if either one of the controls is executed. Hence, it is difficult for a driver of the host vehicle to recognize which one of both of the two controls is executed and the driver may be introduced into a misunderstanding of which one of the controls is executed.
It is, hence, an object of the present invention to provide vehicle velocity control apparatus and method for an automotive vehicle which enable for the vehicle driver to determine accurately which control of either a first following control to be executed during a high-speed run or a second following control to be executed during a low-speed run of the host vehicle is being executed.
According to one aspect of the present invention, there is provided a vehicle velocity control apparatus for an automotive vehicle, comprising: a vehicle velocity detecting section that detects a velocity of the vehicle; a preceding vehicle detecting section that detects a preceding vehicle which is running ahead of the vehicle; a first following vehicle velocity control section that executes a first following control to control the vehicle velocity of the vehicle to make the vehicle velocity of the vehicle substantially equal to a predetermined vehicle velocity when no preceding vehicle is detected and, when the preceding vehicle is detected, to make the vehicle follow the preceding vehicle with the predetermined vehicle velocity as an upper limit on the basis of detected results by the vehicle velocity detecting section and the preceding vehicle detecting section; a first following control start requesting section that requests the first following vehicle velocity control section to start the first following control; a second following vehicle velocity control section that executes a second following control to control the velocity of the vehicle to make the vehicle follow the preceding vehicle when the preceding vehicle is detected on the basis of the detected results by the vehicle velocity detecting section and the preceding vehicle detecting section; a second following control start requesting section that requests the second following vehicle velocity control section to start the second following control: a first request allowing section, included in the first following vehicle velocity control section, that allows the request to start the first following control from the first following control start requesting section when the vehicle velocity of the vehicle detected by the vehicle velocity detecting section falls in a velocity range equal to or higher than a preset first set vehicle velocity; and a second request allowing section, included in the second following vehicle velocity control section, that allows the request to start the second following control from the second control start requesting section when the velocity of the vehicle falls in another velocity range which is equal to or lower than a preset second set vehicle velocity which is lower than the first set vehicle velocity.
According to another aspect of the present invention, there is provided a vehicle velocity control method for an automotive vehicle, comprising: detecting a velocity of the vehicle; detecting a preceding vehicle which is running ahead of the vehicle; executing a first following control to control the vehicle velocity of the vehicle to make the vehicle velocity of the vehicle substantially equal to a predetermined vehicle velocity when no preceding vehicle is detected and, when the preceding vehicle is detected, to make the vehicle follow the preceding vehicle with the predetermined vehicle velocity as an upper limit on the basis of detected results in detecting the vehicle velocity of the vehicle and detecting the preceding vehicle; requesting to start the first following control; executing a second following control to control the velocity of the vehicle to make the vehicle follow the preceding vehicle when the preceding vehicle is detected on the basis of the detected results in detecting the vehicle velocity of the vehicle and detecting the preceding vehicle; requesting to start the second following control; allowing the request to start the first following control when the detected vehicle velocity of the vehicle falls in a velocity range equal to or higher than a preset first set vehicle velocity; and allowing the request to start the second following control when the detected velocity of the vehicle falls in another velocity range which is equal to or lower than a preset second set vehicle velocity which is lower than the first set vehicle velocity.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.